During the production of metallic strip material, it is usual to coil the unfinished strip material into coils and subsequently to unwind the strip material and pass it through a finishing process. This process may involve further rolling of the material. The coils of strip material are positioned in turn on a rotatable mandrel of an uncoiler and the strip is unwound from the coil when it is in position on the mandrel. As the strip material is withdrawn from the coil on the mandrel, the mandrel is rotated and very high rotational speeds may be encountered. If the coil is accurately located on the mandrel, so that the axis of the coil is substantially coaxial with the longitudinal axis of the mandrel, then out-of-balance forces on the mandrel and its supports, as the mandrel is rotated, are reduced to a minimum. If, however, as sometimes occurs, the bore of the coil is damaged or the inner turn of the coil is folded into the bore of the coil, then the coil is positioned eccentrically on the mandrel and, when the mandrel is rotated, the out-of-balance forces on the mandrel and its supports are considerable and damage to the mandrel and to its support bearings can occur.